A PCV (positive crankcase ventilation) system by which blow-by gas leaking from a combustion chamber of an internal combustion engine into a crankcase through a gap between a piston and a cylinder is introduced into an induction system has been conventionally known. The PCV system sends the blow-by gas as incomplete combustion gas into the combustion chamber again, thereby preventing emission of fuel components and carbon monoxide in the blow-by gas into air.
However, the blow-by gas contains an oil component for lubricating the internal combustion engine in mist form, and when the blow-by gas containing the oil component is burnt, disadvantageously, the amount of lubricating oil decreases, and white smoke occurs due to combustion of the oil component. Thus, an oil mist separator is provided in the PCV system to separate the mist oil from the blow-by gas (Refer to, for example, Patent Document 1).
Patent Document 1: JP 2000-310109 A